Accelerated Extraction of PAHs and PCBs Saves Time, Produces Results

Persistent organic pollutants (POPs) are industrially produced compounds that resist decomposition and linger in the environment. Because these compounds can persist in the environment and food chain, permeate phospholipid membranes, and accumulate in fatty tissues, they present significant environmental and health issues. Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) are POPs that have been characterized as both toxic and carcinogenic. Food testing and safety protocols rely upon sensitive, streamlined protocols for the extraction and analysis of solid and semisolid samples. Traditionally, this includes the extraction with solvents and/or sonic vibrations in processes that are both time consuming and result in organic waste. Accelerated solvent extraction, which has been approved for several classes of POPs, including PCBs, has been demonstrated to achieve extraction efficiencies that equal or exceed those accomplished with Soxhlet extraction. It also significantly reduces solvent consumption and time parameters by flexibly combining and automating specific steps of the extraction and analysis processes.   Recently, Murphy et al.¹ reported on the development of a simultaneous extraction method for PAHs and PCBs. The researchers used this method to extract compounds both from spiked mussel tissue and soil samples. For the mussel samples, the researchers used Method 1 conditions on the Dionex ASE 350 (Thermo Scientific): 10MPa (1500 psi) system pressure, 125 degrees temperature, 5 g sample size, 6 minutes oven heat up, 6 minutes static time with 4 static cycles, 30 minute extraction time with Dichloromethane as a solvent. The extracts were then concentrated and a 1 mL aliquot removed for PAH analysis.  Following evaporation with hexane, a 500uL aliquot was removed for PCB analysis. For the soil samples, Method 2 conditions were used: 10MPa (1500 psi) system pressure, 100 degrees temperature, 5 g sample size, 5 minutes oven heat up, 4 minutes static time with 5 static cycles, 25 minute extraction time with Dichloromethane as a solvent. The extracts were concentrated to 5 mL, and 1 mL aliquot was removed for PAH analysis. After solvent exchange to hexane, the extract was diluted for PCB analysis. Gas chromatography mass spectrometry was used to detect PAHs, and gas chromatography with electron capture detection was used to detect PCBs.   The researchers produced results well within the recovery limits set by the EPA. However, it was noted that Method 1 experienced matrix interferences from co-extractable compounds, resulting in the need for frequent cleaning of the injection port. Method 2 reported only negligible co-extractables but demonstrated lower recovery rates for some of the higher molecular weight compounds as compared to Method 1 with its increased extraction temperature. The researchers also noted that the application of alumina to the extraction cell allowed for the production of extracts without matrix interference and saved time during analysis. These findings present real-world applications for the analysis of various products prior to human consumption, including the evaluation of food products for pesticides, herbicides, antibiotics, and contaminants.  Reference

1. Murphy, B. et al. ‘Simultaneous Extraction of PAHs and PCBs from Environmental Samples Using Accelerated Solvent Extraction.’  Thermo Fisher Scientific, Application Note 1025, pp. 1-5.